They won't change out options and stuff.
It is possible for them to use it as a test drive car. It kind of depends on if they have any others in stock.
True story: before I bought mine I had a sales guy tell me that he had a special order coming in on X date and that he would call me before the person who's car it was so that I could test drive it......Guess he didn't care about customers, so naturally I declined and left that dealership.
From what I have seen the average amount of miles on the car when you pick it up is around 8. So that's really the only think you can look for.
Oh, and tell them to take their stupid dealership sticker/badge off of the car while you're away.